PROJECT ABSTRACT Mild traumatic brain injury (mTBI) has been identified as the signature wound of the Iraq and Afghanistan wars.18 MTBI is often associated with chronic cognitive complaints, which have been inconsistently linked to deficits in working memory. Assessments of cognitive complaints and working memory deficits in veterans following combat-related mTBI present numerous challenges because the veteran population represents a cohort with relatively unique characteristics such as mechanism of injury (e.g., blast)19-21 and combat-related psychiatric co-morbidity (i.e., post-traumatic stress disorder; PTSD).19, 22, 23 Functional magnetic resonance imaging (fMRI) provides the opportunity to elucidate neural correlates of working memory performance in mTBI. Directly relating neural activation to behavioral performance provides important context to abnormal neural responses in brain-injured individuals. Modern uses of neuroimaging, such as task-based functional connectivity analyses, permit the investigation of complex cognitive processes (i.e., working memory) by examining interactions of distributed brain regions during task performance. Studies examining the functional connectivity of brain regions during working memory tasks in mTBI are limited, and to our knowledge, no study has examined working memory task-based neural connectivity in veterans with or without mTBI. The current proposal therefore seeks to use advanced, non-invasive, fMRI methods to: (1) investigate whether mTBI veterans exhibit poorer working memory performance than veteran controls; (2) examine brain activation and functional connectivity in mTBI veterans compared to veteran controls; (3) evaluate the association between brain activation, functional connectivity, and working memory performance in mTBI veterans and veteran Controls; and (4) explore the moderation of clinical injury characteristics on the relationship between neural activation or functional connectivity and working memory performance in mTBI veterans. Findings of this proposal will enhance our understanding of clinical characteristics and brain connectivity patterns associated with poor cognitive outcomes following mTBI. Furthermore, understanding the neural correlates of working memory deficits in veterans with mTBI could help provide targets for intervention strategies to help improve cognitive outcomes and quality of life in veterans who have sustained head trauma.